docs: def _copytree(src, dst):
      """Similar to shutils.copytree, except that dst is already there
      """
      try:
          os.makedirs(dst)
      except OSError:
          pass  # It must already exist
      for file in os.listdir(src):
          try:
              shutil.copy2('%s/%s' % (src, file), '%s/%s' % (dst, file))
          except IOError, e:
              try:
                  shutil.copytree('%s/%s' % (src, file), '%s/%s' % (dst, file))
              except OSError:  # Not a directory, reraise copy2 exception
                  raise e